In the Department of Homeland Security’s latest failure to protect the nation, a costly program to place crucial electronic surveillance systems along the U.S.-Mexico border is years behind schedule and grossly over budget because the agency hasn’t adequately managed the contractor doing the work.

As a result, hundreds of millions of taxpayer dollars will be wasted and the porous southern border will continue to be vulnerable despite the Obama Administration’s assurances that it’s as secure as it’s ever been. So far the troubled project, known as Secure Border Initiative Network, has cost the government $672 million although it’s nowhere near completion, according to a new report issued by the investigative arm of Congress (Government Accountability Office).

Launched by Homeland Security in 2005, the initiative aims to enhance border security by designing technological tools that enable Border Patrol agents to detect and respond to incursions along unmanned stretches of the 2,000-mile Mexican border. This includes installing unattended ground sensors, radars and cameras. The so-called virtual fence was supposed to be completed by 2011, but Homeland Security officials recently pushed the date up to 2014.

That’s because the agency has failed to properly oversee the project’s prime contractor, resulting in costly rework, numerous delays and lots of extra money. In fact Homeland Security officials stood by as the contractor provided information that was “replete with unexplained anomalies, thus rendering the data unfit for effective contractor management and oversight,” congressional investigators found.

The initiative to erect barriers—both electronic and physical—along the U.S. Mexico border has been plagued with a multitude of problems since it was implemented under the George W. Bush Administration. After funding issues got largely settled, some border mayors in Texas blocked the feds from conducting fence work on city property, a large Indian tribe (Tohono O’odham) in Arizona refused to allow a fence to be erected along a vulnerable stretch of border and the so-called virtual fence project has been delayed several times.

Last year a separate GAO report revealed that the physical fence is costing U.S. taxpayers an average of nearly $4 million per mile. The per mile costs vary considerably depending on the type of fencing, topography, materials, labor costs and the price of land acquisition, but investigators determined that serious cost overruns have led to the exorbitant average figure.